British strategy in 1777 involved two main prongs of attack, aimed at separating New England (where the rebellion enjoyed the most popular support) from the other colonies. To that end, General John Burgoyne’s army aimed to march south from Canada toward a planned meeting with Howe’s forces on the Hudson River. Burgoyne’s men dealt a devastating loss to the Americans in July by retaking Fort Ticonderoga, while Howe decided to move his troops southward from New York to confront Washington’s army near the Chesapeake Bay. The British defeated the Americans at Brandywine Creek, Pennsylvania, on September 11 and entered Philadelphia on September 25. Washington rebounded to strike Germantown in early October before withdrawing to winter quarters near Valley Forge.
Howe’s move had left Burgoyne’s army exposed near Saratoga, New York, and the British suffered the consequences of this on September 19, when an American force under General Horatio Gates defeated them at Freeman’s Farm (known as the first Battle of Saratoga). After suffering another defeat on October 7 at Bemis Heights (the Second Battle of Saratoga), Burgoyne surrendered his remaining forces on October 17. The American victory Saratoga would prove to be a turning point of the American Revolution, as it prompted France (which had been secretly aiding the rebels since 1776) to enter the war openly on the American side, though it would not formally declare war on Great Britain until June 1778. The American Revolution, which had begun as a civil conflict between Britain and its colonies, had become a world war.